CNN  — 

The two Defense Department civilian workers who were killed when a US sailor opened fire at Pearl Harbor Naval Shipyard earlier this week have been identified.

Vincent J. Kapoi, a metals inspector apprentice, and Roldan A. Agustin, who worked as a shop planner at the naval shipyard, were shot and killed on Wednesday, Joint Base Pearl Harbor-Hickman officials said in a statement.

Kapoi’s sister, Theona Kapoi, described her brother as “easy-going, fun-loving, ‘let’s do this’ man.”

“There are so many unanswered questions. We all have to be honest: It changes nothing, because we can’t bring him back. What we do have to do, and we must do, is honor his memory, keep him alive in our hearts – and please keep him in your hearts, and always remember good times,” Theona Kapoi said in a statement Friday.

A third victim who was injured during the shooting remains hospitalized in critical condition, Norman Dominesey, Naval Criminal Investigative Service special agent in charge, told reporters on Friday.

Gabriel Antonio Romero, an active-duty US Navy sailor, opened fire at the Pearl Harbor Naval shipyard on Wednesday, US Navy officials said.

Within 23 seconds, he shot three civilian workers and killed himself, Dominesey said.

Romero, who was from Texas, was a machinist’s mate auxiliary fireman assigned to the USS Columbia attack submarine. The submarine was in a dry dock at the base for standard maintenance work.

The US sailor enlisted in December 2017 and completed boot camp and then the Navy’s submarine school on June 2018. He submarine was his first duty station, according to biographical data provided by the US Navy.

Authorities were still investigating a possible motive on Friday but officials do not believe the shooting was associated with terrorism.

“At this time this act does not appear to have been motivated by any particular ideology,” FBI Special Agent Sam Miranda told reporters.

Security stands guard outside the main gate at Joint Base Pearl Harbor-Hickam, in Hawaii.

Miranda said it appears that Romero acted alone.

The shooting took place just three days before National Pearl Harbor Remembrance Day, when the nation commemorates those who died in the December 7, 1941, Japanese attack on Pearl Harbor that thrust the United States into World War II.

It was 78 years ago Saturday that the Imperial Japanese Navy attacked Pearl Harbor, killing more than 2,000 Americans and destroying a significant share of US battleships and airplanes.

An annual commemoration ceremony at the Pearl Harbor Visitor Center is expected to take place as planned on Saturday, a spokeswoman for the Pearl Harbor National Memorial said.

CNN’s Barbara Starr and Melissa Alonso contributed to this report.